Advanced Sensor Technologies, Inc. (AST) proposes to continue its NIH funded Phase I efforts to develop a completely automated miniaturized device capable of monitoring different types of cholinesterases from a single drop of whole blood to determine the degree of exposure of an individual to organophosphate (OP) compounds or carbamates. This device will be amenable to mass screening of pesticide workers, persons in direct contact with OP compounds, as well as soldiers and civilians potentially exposed to chemical warfare agents. Towards these goals, AST has developed a passive first generation micro-electro-mechanical system (MEMS) based prototype with integrated fluid acquisition and external monitoring system, and has performed tests to prove its feasibility in monitoring cholinesterase activity. AST is requesting Phase II funding to improve the Phase I prototype and develop a commercially available, completely automated device, suitable for the general population. Cholinesterase activity in blood is affected by OP compounds and carbamates, with the level of exposure inversely proportional to the toxin concentration or activity. Different types of cholinesterases are located in plasma and red blood cells, and monitoring these blood enzymes automatically, in finger-prick samples of blood, by an untrained individual, will require miniaturization and integration of several different components.